The present invention relates to the field of semiconductor devices. More specifically, the present invention relates to tunable work function for RMG integration.
High-k metal gate technology has changed the way a silicon (Si) transistor is built. It is one of the most significant innovations in the last few decades, enabling the continued scaling of microprocessors and providing significant power and performance benefits. In high-k metal gate technology, the silicon oxide insulator and poly-silicon electrode from the transistor are replaced by a high dielectric constant (k) insulator and metal electrode. The development of high-k and metal gates has led to improved performance of key features, including: work function control, thermal stability, high mobilities, reduced nanoscale variability, enhanced AC performance, and dielectric reliability.
There are several challenges that exist as semiconductor devices are scaled down, one of which involves choosing the materials to use for the gate dielectric and electrode. Selecting which gate to use usually involves factoring in resisitivity and work function. Currently, the replacement metal gate (RMG) approach is becoming the industry standard. RMG technology has a number of advantages over gate-first integration, which allows for improved device performance and provides the fabricator with additional options to select from for the gate metal and high-k materials. Several other advantages of RMG are improved short channel control, improved work function tuning, and lower gate resistance.